Turbo type fluid machine

ABSTRACT

A turbo type compressor of the present invention comprises a housing, a rotating shaft, and first and second impellers. The rotating shaft is supported by the housing to be rotatable around a rotational axis. A cylinder portion is provided on the rear end side of the rotating shaft. The rotating shaft is supported by a first radial foil bearing provided on the radially outer circumference of the cylinder portion and a second radial foil bearing provided on the radially inner circumference of the cylinder portion.

TECHNICAL FIELD

The present invention relates to a turbo type fluid machine.

BACKGROUND ART

Japanese Patent Application Laid-Open No. 2009-257165 discloses a conventional turbo type fluid machine. The turbo type fluid machine includes a rotating shaft supported by a housing to be rotatable around a rotational axis and an impeller coupled to the rotating shaft. In the turbo type fluid machine, fluid is discharged by rotation of the impeller. The rotating shaft is supported by two radial foil bearings provided in the front and the rear in a rotational axis direction.

The radial foil bearings include top foils located on the outer circumference side of the rotating shaft and bump foils located on the outer circumference sides of the top foils and capable of elastically supporting the top foils.

In the radial foil bearings, when the rotational speed of the rotating shaft is low, the outer circumferential surface of the rotating shaft and the top foils slide with each other. On the other hand, when the rotational speed of the rotating shaft increases, since the dynamic pressure of the fluid acts between the outer circumferential surface of the rotating shaft and the top foils, the outer circumferential surface of the rotating shaft and the top foils change into a noncontact state in the radial direction. The rotating shaft rotates at a low coefficient of friction in the radial direction. Therefore, the turbo type fluid machine achieves high power performance. A wear of rotating shaft and the like are less in the radial direction. Therefore, the turbo type fluid machine achieves high durability.

However, when the turbo type fluid machine explained above is mounted on, for example, a vehicle, it is likely that the rotating shaft is swung by vibration or the like and the dynamic pressure is less effective on the radial foil bearings. In this case, the outer circumferential surface of the rotating shaft may be brought into contact with the radial foil bearings, and not only noise and vibration may occur in the radial foil bearings and the rotating shaft but also the wear may occur to spoil durability.

Therefore, in order to increase a load capacity of the radial foil bearings by increasing the area of a portion where the dynamic pressure occurs, the lengths in the rotational axis direction of the rotating shaft and the radial foil bearings may be increased or the radiuses thereof may be increased, which, however, increases the size of the turbo type fluid machine. In this case, for example, mounting performance on a vehicle or the like is spoiled.

The present invention has been devised in view of the conventional circumstances, and it is an object of the invention to provide a turbo type fluid machine that less easily causes noise and vibration and is capable of achieving excellent durability while realizing a reduction in size.

SUMMARY OF THE INVENTION

A turbo type fluid machine of the present invention is a turbo type fluid machine comprising: a rotating shaft supported by a housing to be rotatable around a rotational axis; and an impeller coupled to the rotating shaft. The turbo type fluid machine discharges fluid along with rotation of the impeller. The rotating shaft includes a cylinder portion. The rotating shaft is supported by a first radial foil bearing provided on the radially outer circumference of the cylinder portion and a second radial foil bearing provided on the radially inner circumference of the cylinder portion.

Other aspects and advantages of the present invention will be apparent from the embodiments disclosed in the following description and the attached drawings, the illustrations exemplified in the drawings, and the concept of the invention disclosed in the entire description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a turbo type compressor in an embodiment 1.

FIG. 2 is an A-A sectional view of FIG. 1, according to the turbo type compressor in the embodiment 1.

FIG. 3 is a B-B sectional view of FIG. 1, according to the turbo type compressor in the embodiment 1.

FIG. 4 is a schematic diagram showing a control mechanism, according to the turbo type compressor in the embodiment 1.

FIG. 5 is a sectional view of a turbo type compressor in an embodiment 2.

FIG. 6 is a B-B sectional view of FIG. 1 of the turbo type compressor in which a first radial foil including three keys and a second radial foil including two keys are provided, according to the turbo type compressor in the embodiment 3.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments 1 to 3 embodying the present invention are explained below with reference to the drawings.

Embodiment 1

As shown in FIG. 1, a turbo type compressor 100, which is a turbo type fluid machine, includes a housing 1, a rotating shaft 3 having a rotational axis O as a center axis, an electric motor 5, a first impeller 7, and a second impeller 9.

The housing 1 includes a front housing 11, an end plate 13, and a rear housing 15.

The front housing 11 includes a first front housing 11 a, a second front housing 11 b, a third front housing 11 c, and a fourth front housing 11 d. In the front housing 11, the first front housing 11 a, the second front housing 11 b, the third front housing 11 c, and the fourth front housing 11 d are joined in this order from the front end side toward the rear end side. In the front housing 11, first and second impeller chambers 17 and 19, first and second diffusers 21 and 23, first and second discharge chambers 25 and 27, a motor chamber 29, first and second suction ports 31 and 33, an intermediate pressure port 35, and a discharge port 37 are formed. In the second front housing 11 b, a first shaft hole 41 a extending in the rotational axis O direction is formed.

The first impeller chamber 17 is formed on the front end side of the front housing 11. The first impeller chamber 17 is formed by the first front housing 11 a and the second front housing 11 b. The first impeller chamber 17 is formed in a circular truncated cone shape curved such that a generatrix approaches the rotational axis O from the rear side toward the front side of the front housing 11.

The second impeller chamber 19 is formed further in the rear than the first impeller chamber 17 in the front housing 11. The second impeller chamber 19 is formed by the second front housing 11 b and the third front housing 11 c. The second impeller chamber 19 is formed in a circular truncated cone shape curved such that a generatrix approaches the rotational axis O from the front side toward the rear side of the front housing 11. The second impeller chamber 19 is formed in a similar shape smaller than the first impeller chamber 17.

The first diffuser 21 is formed on the front end side of the second front housing 11 b and located on the outer circumference side of the first impeller chamber 17. The first diffuser 21 communicates with the first impeller chamber 17 in a part where the inner diameter of the first impeller chamber 17 is the largest.

The second diffuser 23 is formed on the front end side of the third front housing 11 c and located on the outer circumference side of the second impeller chamber 19. The second diffuser 23 communicates with the second impeller chamber 19 in a part where the inner diameter of the second impeller chamber 19 is the largest. The second diffuser 23 is formed in a diameter smaller than the first diffuser 21.

The first discharge chamber 25 is formed by the first front housing 11 a and the second front housing 11 b. The first discharge chamber 25 is located on the outer circumference side of the first diffuser 21 and communicates with the first diffuser 21. The first discharge chamber 25 is an annular space and is formed such that the sectional area thereof gradually enlarges in the rotational axis O direction. The first discharge chamber 25 communicates with the first impeller chamber 17 via the first diffuser 21.

The second discharge chamber 27 is formed by the second front housing 11 b and the third front housing 11 c. The second discharge chamber 27 is located on the outer circumference side of the second diffuser 23 and communicates with the second diffuser 23. The second discharge chamber 27 is an annular space and is formed such that the sectional area thereof gradually enlarges in the rotational axis O direction. Since the second impeller chamber 19 and the second diffuser 23 are respectively smaller in diameter than the first impeller chamber 17 and the first diffuser 21, the second discharge chamber 27 is located further on the inner circumference side of the front housing 11 than the first discharge chamber 25. The second discharge chamber 27 communicates with the second impeller chamber 19 via the second diffuser 23.

The second discharge chamber 27 communicates with the discharge port 37. The discharge port 37 is formed by the second front housing 11 b and the third front housing 11 c and radially extends from the second discharge chamber 27. The discharge port 37 causes the second discharge chamber 27 and the outside of the front housing 11 to communicate with each other.

The motor chamber 29 is formed in the fourth front housing 11 d. The motor chamber 29 extends in the rotational axis O direction.

In the fourth front housing 11 d, a boss 51 is formed on the front end side of the motor chamber 29. The boss 51 extends toward the rear end side of the motor chamber 29 in the rotational axis O direction. A second shaft hole 51 a coaxial with the first shaft hole 41 a is formed in the boss 51. A third radial foil bearing 43 is provided in the second shaft hole 51 a.

The first suction port 31 is formed on the front end side of the first front housing 11 a. The first suction port 31 extends in the rotational axis O direction. The front end side of the first suction port 31 opens to the front end surface of the first front housing 11 a. The rear end side of the first suction port 31 communicates with the first impeller chamber 17.

The second suction port 33 is formed to extend across the rear end side of the third front housing 11 c and the front end side of the fourth front housing 11 d. The rear end side of the second suction port 33 communicates with the motor chamber 29 on the front end side of the boss 51. On the other hand, the front end side of the second suction port 33 communicates with the second impeller chamber 19. The second suction port 33 communicates with the second shaft hole 51 a. That is, the second suction port 33 causes the motor chamber 29 and the second impeller chamber 19 to communicate with each other.

The intermediate pressure port 35 is formed further on the outer circumference side than the second discharge chamber 27 to extend across the second to fourth front housings 11 b, 11 c, and 11 d in the rotational axis O direction. The front end of the intermediate pressure port 35 communicates with the first discharge chamber 25. The rear end of the intermediate pressure port 35 communicates with the motor chamber 29. That is, the intermediate pressure port 35 causes the first discharge chamber 25 and the motor chamber 29 to communicate with each other in the rotational axis O direction.

The end plate 13 is joined to the rear end of the fourth front housing 11 d. That is, the end plate 13 closes the rear end of the motor chamber 29. In the endplate 13, a third shaft hole 13 a coaxial with the first and second shaft holes 41 a and 51 a is formed. A third shaft supporting surface 13 b orthogonal to the rotational axis O is formed at the rear end of the end plate 13. A third key groove 13 c, which extends in a direction orthogonal to the rotational axis O, is recessed in the third shaft supporting surface 13 b.

The rear housing 15 is located in the rear of the housing 1 and jointed to the rear end side of the end plate 13. The rear housing 15 sandwiches the endplate 13 in conjunction with the fourth front housing 11 d. The rear housing 15 includes a columnar convex portion 15 a extending front from the rear in the rotational axis O direction. A fourth shaft supporting surface 15 b orthogonal to the rotational axis O and facing the third shaft supporting surface 13 b is formed at the front end of the convex portion 15 a. A fourth key groove 15 t, which extends in a direction orthogonal to the rotating shaft 3, is recessed in the fourth shaft supporting surface 15 b. The rear housing 15 corresponds to a bottomed cylindrical portion.

In the rear housing 15, an annular radial space 15 c extending in the rotational axis O direction to surround the outer circumference of the convex portion 15 a and a disk-shaped thrust space 15 d linked to the front end of the radial space 15 c and formed by the rear housing 15 and the end plate 13 are formed. The front end of the radial space 15 c and the thrust space 15 d communicate with each other.

A first shaft supporting surface 15 f coaxial with the rotational axis O is formed on the inner circumferential surface of the rear housing 15, that is, the outer circumferential surface of the radial space 15 c. A second shaft supporting surface 15 e coaxial with the rotational axis O and located further on the rotational axis O side than the first shaft supporting surface 15 f is formed on the outer circumferential surface of the convex portion 15 a, that is, the inner circumferential surface of the radial space 15 c. As shown in FIG. 3, a first key groove 15 g, which extends in the rotational axis O direction, is recessed in the first shaft supporting surface 15 f. A second key groove 15 h, which extends in the rotational axis O direction, is recessed in the second shaft supporting surface 15 e.

As shown in FIG. 1, the rotating shaft 3 includes a rotating shaft main body 3 a, a small diameter portion 3 b integrated with the rotating shaft main body 3 a and located on the front end side of the rotating shaft main body 3 a, and a cylinder portion 3 c located on the rear end side of the rotating shaft main body 3 a. The rotating shaft main body 3 a is formed in a columnar shape. The small diameter portion 3 b is formed in a columnar shape smaller in diameter than the rotating shaft main body 3 a.

The rotating shaft 3 is inserted through the housing 1 and supported to be rotatable around the rotational axis O. The front end side of the rotating shaft main body 3 a is inserted through the second shaft hole 51 a and rotatably supported by the third radial foil bearing 43. On the other hand, the rear end side of the rotating shaft main body 3 a is inserted through a third shaft hole 13 a. A gap 73, into which a refrigerant serving as fluid can be flowed, is provided between the rotating shaft main body 3 a and the third shaft hole 13 a. The small diameter portion 3 b is inserted through the first shaft hole 41 a.

The cylinder portion 3 c includes a disk-shaped first supported portion 55 extending from the rear end of the rotating shaft main body 3 a in a direction orthogonal to the rotational axis O and a cylindrical second supported portion 53 extending rearward, further apart from the rear end of the rotating shaft main body 3 a, from the outer circumferential edge of the first supported portion 55 in parallel with the rotational axis O. The second supported portion 53 and the first supported portion 55 are integrated. The cylinder portion 3 c is opened on the rear end side of the second supported portion 53 and is formed in a bottomed cylindrical shape having the first supported portion 55 as a bottom.

The electric motor 5 is provided in the motor chamber 29. The electric motor 5 includes a stator 5 a and a rotor 5 b. The stator 5 a is fixed to the inner wall of the motor chamber 29. The stator 5 a is electrically connected to a not-shown battery. The rotor 5 b is located on the inner circumference side of the stator 5 a. The rotor 5 b is fixed to the rotating shaft main body 3 a.

The first impeller 7 is press-fit into the front end side of the small diameter portion 3 b in the rotating shaft 3 and provided in the first impeller chamber 17. The first impeller 7 is capable of rotating in the first impeller chamber 17 along with the rotation of the rotating shaft 3. The first impeller 7 is formed in a circular truncated cone shape curved such that a generatrix approaches the rotational axis O. In the first impeller 7, a plurality of blades 70 are provided at a predetermined interval. A portion formed in a small diameter of the first impeller 7 is located at the front end of the small diameter portion 3 b. A portion formed in a large diameter of the first impeller 7 is located near the motor chamber 29.

The second impeller 9 is press-fit into the rear end side of the small diameter portion 3 b in the rotating shaft 3 and provided in the second impeller chamber 19. The second impeller 9 is capable of rotating in the second impeller chamber 19 along with the rotation of the rotating shaft 3. The second impeller 9 is formed in a circular truncated cone shape curved such that a generatrix approaches the rotational axis O. The second impeller 9 is formed in a shape similar to the shape of the first impeller 7. A portion formed in a small diameter of the second impeller 9 is located at the rear end of the small diameter portion 3 b. A portion formed in a large diameter of the second impeller 9 is located near the first impeller 7. That is, in the front housing 11, the portion formed in the large diameter of the first impeller 7 and the portion formed in the large diameter of the second impeller 9 are arranged to face each other. In the second impeller 9, a plurality of blades 90 are provided at a predetermined interval.

On the outer circumference side of the second supported portion 53, a first shaft supported surface 53 a coaxial with the rotational axis O and facing the first shaft supporting surface 15 f is formed. A first radial foil bearing 57 is provided between the first shaft supporting surface 15 f and the first shaft supported surface 53 a. The first radial foil bearing 57 is installed to the inner circumferential surface of the rear housing 15, that is, the first shaft supporting surface 15 f.

The first radial foil bearing 57 includes, as shown in FIG. 3, a first top foil 57 a located on the outer circumference side of the first shaft supported surface 53 a and displaceable with respect to the first shaft supporting surface 15 f and a first bump foil 57 b located on the outer circumference side of the first top foil 57 a and displaced with respect to the first shaft supporting surface 15 f to be capable of elastically supporting the first top foil 57 a.

As the first top foil 57 a, a metal thin plate is curved in a substantially arc shape. The first top foil 57 a includes one gap 57 s slenderly extending in the front-rear direction. The first top foil 57 a is located on the outer circumference side of the second supported portion 53 and surrounds the first shaft supported surface 53 a.

At one end of the first top foil 57 a, a first key 57 k engaged in the first key groove 15 g is formed. The first key 57 k is a small piece projecting from the end edge of the first top foil 57 a, which forms the gap 57 s, in the radial outer direction. The first key 57 k engages in the first key groove 15 g to thereby stop or prevent rotation of the first top foil 57 a in a radial space 15 c. The other end of the first top foil 57 a is formed as a free end. The first key 57 k corresponds to a first rotation stop portion.

As the first bump foil 57 b, a metal thin plate, on which a plurality of curved portions 57 w are formed, is curved in a substantially arc shape. The first bump foil 57 b is elastically deformed to crush the curved portions 57 w or is restored to the original shape to thereby be displaced with respect to the first shaft supporting surface 15 f to be capable of elastically supporting the first top foil 57 a.

On the inner circumference side of the second supported portion 53, a second shaft supported surface 53 b coaxial with the rotational axis O and facing the second shaft supporting surface 15 e is formed. A second radial foil bearing 59 is provided between the second shaft supporting surface 15 e and the second shaft supported surface 53 b. The second radial foil bearing 59 is installed to the outer circumferential surface of the convex portion 15 a in the rear housing 15, that is, the second shaft supporting surface 15 e.

The second radial foil bearing 59 includes a second top foil 59 a located on the outer circumference side of the second shaft supporting surface 15 e and displaceable with respect to the second shaft supporting surface 15 e and a second bump foil 59 b located on the inner circumference side of the second top foil 59 a and displaced with respect to the second shaft supporting surface 15 e to be capable of elastically supporting the second top foil 59 a.

As the second top foil 59 a, a metal thin plate is curved in a substantially arc shape. The second top foil 59 a includes one gap 59 s slenderly extending in the front-rear direction. The second top foil 59 a is located on the inner circumferential side of the second supported portion 53 and surrounds the second shaft supporting surface 15 e.

At one end of the second top foil 59 a, a second key 59 k engaged in the second key groove 15 h is formed. The second key 59 k is a small piece projecting from the end edge of the second top foil 59 a, which forms the gap 59 s, in the radial inner direction. The second key 59 k engages in the second key groove 15 h to thereby stop of prevent rotation of the second top foil 59 a in the radial space 15 c. The other end of the second top foil 59 a is formed as a free end. The second key 59 k corresponds to a second rotation stop portion.

As the second bump foil 59 b, a metal thin plate, on which a plurality of curved portions 59 w are formed, is curved in a substantially arc shape. The second bump foil 59 b is elastically deformed to crush the respective curved portions 59 w or restored to the original shape to thereby be displaced with respect to the second shaft supporting surface 15 e to be capable of elastically supporting the second top foil 59 a.

The first key 57 k and the second key 59 k shift from each other by about 45° centering on the rotational axis O. Therefore, the first key 57 k and the second key 59 k and the rotational axis O are respectively arranged such that the rotational axis O does not cross an imaginary straight line L1 that connects the first key 57 k and the second key 59 k, or is absent on the imaginary straight line L1 that connects the first key 57 k and the second key 59 k.

As shown in FIG. 1, on the front end side of the first supported portion 55, a third shaft supported surface 55 a orthogonal to the rotational axis O and facing the third shaft supporting surface 13 b is formed. A first thrust foil bearing 61 is provided between the third shaft supporting surface 13 b and the third shaft supported surface 55 a. The first thrust foil bearing 61 is installed to the rear end side of the end plate 13, that is, the third shaft supporting surface 13 b.

On the rear end side of the first supported portion 55, a fourth shaft supported surface 55 b orthogonal to the rotational axis O and facing the fourth shaft supporting surface 15 b is formed. A second thrust foil bearing 63 is provided between the fourth shaft supporting surface 15 b and the fourth shaft supported surface 55 b. The second thrust foil bearing 63 is installed to the front end side of the convex portion 15 a in the rear housing 15, that is, the fourth shaft supporting surface 15 b. The first thrust foil bearing 61 is provided on the one end side of the first supported portion 55, which is the side near the first and second impellers 7 and 9, and the second thrust foil bearing 63 is provided on the other end side of the first supported portion 55.

As shown in FIG. 2, the first thrust foil bearing 61 includes eight third top foils 61 a located on one end side of the third shaft supported surface 55 a and displaceable with respect to the third shaft supporting surface 13 b and eight third bump foils 61 b located on one end sides of the respective third top foils 61 a and displaced with respect to the third shaft supporting surface 13 b to be capable of elastically supporting the respective third top foils 61 a.

The respective third top foils 61 a are made of metal thin plates and arranged radially from the rotational axis O. Gaps 61 s in eight places slenderly extending radially from the rotational axis O are provided among the respective third top foils 61 a. The respective third top foils 61 a are located on the front end side of the third shaft supported surface 55 a. In other words, the respective third top foils 61 a are located on the rear end side of the third shaft supporting surface 13 b.

At one ends of the respective third top foils 61 a, as shown in FIG. 1 and FIG. 2, third keys 13 k engaged in the third key grooves 13 c are formed. The third keys 13 k are small pieces projecting from the end edges of the respective third top foils 61 a, which form the gaps 61 s, toward the end plate 13 in the rotational axis O direction. The respective third keys 13 k engage in the respective third key grooves 13 c to thereby stop rotation of the respective third top foils 61 a in the thrust space 15 d. The other ends of the respective third top foils 61 a are formed as free ends.

The respective third bump foils 61 b are wavy plate-shaped metal thin plates on which a plurality of curved portions are formed. The respective third bump foils 61 b are elastically deformed to crush the curved portions or restored to the original shape to thereby be displaced with respect to the respective third shaft supporting surfaces 13 b and capable elastically supporting the respective third top foils 61 a.

The second thrust foil bearing 63 includes eight fourth top foils 63 a located on one end side of the fourth shaft supporting surface 15 b and displaceable with respect to the fourth shaft supporting surface 15 b and eight fourth bump foils 63 b located on the other end side of the fourth top foils 63 a and displaced with respect to the fourth shaft supporting surface 15 b to be capable of elastically supporting the fourth top foils 63 a.

The respective fourth top foils 63 a are made of metal thin plates and arranged radially from the rotational axis O. Gaps 63 s in eight places slenderly extending radially from the rotational axis O are provided among the respective fourth top foils 63 a. The respective fourth top foils 63 a are located on the rear end side of the fourth shaft supported surface 55 b. In other words, the respective fourth top foils 63 a are located on the front end side of the fourth shaft supporting surface 15 b.

At one ends of the respective fourth top foils 63 a, fourth keys 15 k engaged in the fourth key grooves 15 t are formed. The fourth keys 15 k are small pieces projecting from the end edges of the respective fourth top foils 63 a, which form the gaps 63 s, toward the convex portion 15 a in the rotational axis O direction. The respective fourth keys 15 k engage in the respective fourth key grooves 15 t to thereby stop rotation of the respective fourth top foils 63 a in the thrust space 15 d. The other ends of the respective fourth top foils 63 a are formed as free ends.

The respective fourth bump foils 63 b are wavy plate-shaped metal thin plates on which a plurality of curved portions are formed. The respective fourth bump foils 63 b are elastically deformed to crush the curved portions or restored to the original shape to thereby be displaced with respect to the respective fourth shaft supporting surfaces 15 b to be capable of elastically supporting the respective fourth top foils 63 a.

In the turbo type compressor 100, as shown in FIG. 4, a pipe 103 connected to a condenser 101 is connected to the discharge port 37. The condenser 101 is connected to an evaporator 109 via a pipe 105 and an expansion valve 107. The evaporator 109 is connected to the first suction port 31 through a pipe 111. A refrigeration circuit of an air-conditioning apparatus for a vehicle is configured by the turbo type compressor 100, the evaporator 109, the expansion valve 107, the condenser 101, and the like.

In the turbo type compressor 100 configured as explained above, a driving force for rotating the rotor 5 b around the rotational axis O is generated by energization to the stator 5 a and the rotating shaft 3 rotates. Consequently, the first impeller 7 rotates in the first impeller chamber 17. The second impeller 9 rotates in the second impeller chamber 19. Therefore, the refrigerant passed through the evaporator 109 is sucked from the first suction port 31 through the pipe 111 and reaches the first impeller chamber 17.

The first impeller 7 rotates in the first impeller chamber 17 to thereby increase kinetic energy of the refrigerant in the first impeller chamber 17. The first impeller 7 converts, through the first diffuser 21, the kinetic energy of the refrigerant into pressure energy to compress the refrigerant and discharges the compressed refrigerant to the first discharge chamber 25. Consequently, the pressure of the refrigerant in the first discharge chamber 25 changes to an intermediate pressure. The refrigerant having the intermediate pressure circulates from the first discharge chamber 25 to the intermediate pressure port 35 and flows into the motor chamber 29 as indicated by a solid line arrow in FIG. 1.

The refrigerant flown into the motor chamber 29 is sucked from the second suction port 33 into the second impeller chamber 19 as indicated by a solid line arrow. In this case, the refrigerant circulating through the second suction port 33 is sucked into the second impeller chamber 19. The second impeller 9 rotates in the second impeller chamber 19 to thereby increase kinetic energy of the refrigerant in the second impeller chamber 19. The second impeller 9 converts, through the second diffuser 23, the kinetic energy of the refrigerant into pressure energy to compress the refrigerant and discharges the refrigerant to the second discharge chamber 27. The refrigerant in the second discharge chamber 27 is discharged from the discharge port 37 to the condenser 101. The refrigerant passes through the expansion valve 107 and the evaporator 109 and is again sucked into the first impeller chamber 17 from the first suction port 31. In this way, cooling of a vehicle interior is performed.

While the cooling is performed, in the turbo type compressor 100, since the refrigerant flown in from the intermediate pressure port 35 is led to the motor chamber 29, it is possible to cool the electric motor 5 that generates heat during actuation.

In the turbo type compressor 100, the refrigerant flowing to the motor chamber 29 passes through the gap 73 and flows into the thrust space 15 d. The refrigerant flown into the thrust space 15 d can flow into a space between the third shaft supported surface 55 a and the third shaft supporting surface 13 b, a space between the first shaft supported surface 53 a of the radial space 15 c and the first shaft supporting surface 15 f, a space between the second shaft supported surface 53 b and the second shaft supporting surface 15 e, and a space between the fourth shaft supported surface 55 b and the fourth shaft supporting surface 15 b in order.

In the turbo type compressor 100, in FIG. 1 and FIG. 3, when the rotational speed of the rotating shaft 3 is low, the first shaft supported surface 53 a and the first radial foil bearing 57 slide with each other and the second shaft supported surface 53 b and the second radial foil bearing 59 slide with each other. On the other hand, when the rotational speed of the rotating shaft 3 increases, the dynamic pressure of the refrigerant acts between the first shaft supported surface 53 a of the second supported portion 53 in the rotating shaft 3 and the first top foil 57 a in the first radial foil bearing 57. The dynamic pressure of the refrigerant also acts between the second shaft supported surface 53 b of the second supported portion 53 and the second top foil 59 a in the second radial foil bearing 59. With the dynamic pressure, the first and second top foils 57 a and 59 a displace with respect to the first and second shaft supporting surfaces 15 f and 15 e. The first and second bump foils 57 b and 59 b displace with respect to the first and second shaft supporting surface 15 f and 15 e and elastically support the first and second top foils 57 a and 59 a. Consequently, the first shaft supported surface 53 a and the first top foil 57 a separate from each other and the second shaft supported surface 53 b and the second top foil 59 a separate from each other. That is, the second supported portion 53 of the rotating shaft 3 and the first and second top foils 57 a and 59 a separate from each other. In this way, the first and second shaft supported surfaces 53 a and 53 b are supported by the first and second radial foil bearings 57 and 59 in a noncontact state.

In this case, in the turbo type compressor 100, the rotational axis O is absent on the imaginary straight line L1 that connects the first key 57 k of the first top foil 57 a in the first radial foil bearing 57 and the second key 59 k of the second top foil 59 a in the second radial foil bearing 59.

Therefore, in the turbo type compressor 100, even if the refrigerant flows out from the gap 57 s of the first top foil 57 a and the dynamic pressure of the refrigerant is less effective between the first shaft supported surface 53 a and the first top foil 57 a, the dynamic pressure of the refrigerant acts between the second shaft supported surface 53 b and the second top foil 59 a located on an imaginary straight line that connects the gap 57 s and the rotational axis O. In the turbo type compressor 100, even if the refrigerant flows out from the gap 59 s of the second top foil 59 a and the dynamic pressure of the refrigerant is less effective between the second shaft supported surface 53 b and the second top foil 59 a, the dynamic pressure of the refrigerant acts between the first shaft supported surface 53 a and the first top foil 57 a located on a straight line that connects the gap 59 s and the rotational axis O.

Therefore, even if the first shaft supported surface 53 a of the second supported portion 53 in the rotating shaft 3 approaches the gap 57 s of the first top foil 57 a, the second shaft supported surface 53 b of the second supported portion 53 hardly approaches the gap 59 s of the second top foil 59 a.

The rotating shaft 3 rotates at a low coefficient of friction in the radial direction. Therefore, the turbo type compressor 100 achieves high power performance. The wear of the rotating shaft 3 and the like are less in the radial direction. Therefore, the turbo type compressor 100 achieves high durability.

In the turbo type compressor 100, in FIG. 1 and FIG. 2, when the rotational speed of the rotating shaft 3 is low, the third shaft supported surface 55 a and the first thrust foil bearing 61 slide with each other and the fourth shaft supported surface 55 b and the second thrust foil bearing 63 slide with each other. On the other hand, when the rotational speed of the rotating shaft 3 increases, the dynamic pressure of the refrigerant acts between the third shaft supported surface 55 a of the first supported portion 55 in the rotating shaft 3 and the third top foil 61 a in the first thrust foil bearing 61. The dynamic pressure of the refrigerant also acts between the fourth shaft supported surface 55 b of the first supported portion 55 and the fourth top foil 63 a in the second thrust foil bearing 63. With the dynamic pressure, the third and fourth top foils 61 a and 63 a displace with respect to the third and fourth shaft supporting surfaces 13 b and 15 b. The third and fourth bump foils 61 b and 63 b displace with respect to the third and fourth shaft supporting surfaces 13 b and 15 b and elastically support third and fourth top foils 61 a and 63 a. Consequently, the third shaft supported surface 55 a and the third top foil 61 a separate from each other and the fourth shaft supported surface 55 b and the fourth top foil 63 a separate from each other. That is, the first supported portion 55 of the rotating shaft 3 and the third and fourth top foils 61 a and 63 a separate from each other. In this way, the third and fourth shaft supported surfaces 55 a and 55 b are supported by the first and second thrust foil bearings 61 and 63 in a noncontact state.

Further, in the turbo type compressor 100, even if the rotating shaft 3 is swung by vibration or the like, the dynamic pressure acts in each of the first and second radial foil bearings 57 and 59 and the first and second thrust foil bearings 61 and 63. The area of a portion where the dynamic pressure is generated is large compared with the conventional turbo type compressor. That is, load capacities of the first and second radial foil bearings 57 and 59 and the first and second thrust foil bearings 61 and 63 are large.

In particular, in the first and second radial foil bearings 57 and 59, the rotating shaft 3 easily changes to the noncontact state with respect to the first and second shaft supported surfaces 53 a and 53 b of the second supported portion 53 in the radial direction by the dynamic pressure generated on the inner side and the dynamic pressure generated on the outer side, that is, the dynamic pressure generated on the first shaft supported surface 53 a and the dynamic pressure generated on the second shaft supported surface 53 b.

Therefore, in the turbo type compressor 100, in the radial direction, noise and vibration are less easily caused on the first and second shaft supporting surfaces 15 f and 15 e and the first and second shaft supported surfaces 53 a and 53 b and the wear is less easily caused.

In the turbo type compressor 100, since the second thrust foil bearing 63 is located in the cylinder portion 3 c of the rotating shaft 3, it is possible to reduce the length in the rotational axis O direction by at least the thickness of the second thrust foil bearing 63. Therefore, in the turbo type compressor 100, an increase in the size of the housing 1 is suppressed.

Therefore, the turbo type compressor 100 less easily causes noise and vibration and is capable of achieving excellent durability while realizing a reduction in size.

In the turbo type compressor 100, the first radial foil bearing 57 is provided between the first shaft supporting surface 15 f and the first shaft supported surface 53 a. The second radial foil bearing 59 is provided between the second shaft supporting surface 15 e and the second shaft supported surface 53 b. In the turbo type compressor 100, since the first and second radial foil bearings 57 and 59 are adopted, management of the gaps formed between the first and second radial foil bearings 57 and 59 and the first and second shaft supported surfaces 53 a and 53 b is simplified. Therefore, in the turbo type compressor 100, it is easy to install together the first and second radial foil bearings 57 and 59.

In the turbo type compressor 100, the cylinder portion 3 c of the rotating shaft 3 is inserted between the first radial foil bearing 57 provided on the radially inner circumference of the rear housing 15 and the second radial foil bearing 59 provided on the radially outer circumference of the convex portion 15 a. Therefore, the installation of the cylinder portion 3 c can be easy.

Embodiment 2

As shown in FIG. 5, in an end plate 213, a boss 214 extending toward the motor chamber 29 in the rotational axis O direction is formed. In the boss 214, a third shaft hole 213 a extending in the rotational axis O direction is formed. In the third shaft hole 213 a, a first shaft supporting surface 215 f coaxial with the rotational axis O is formed. A first radial foil bearing 257 is provided on the first shaft supporting surface 215 f. A gap 214 s is present between the front end side of the boss 214 and the rear end side of the rotor 5 b.

On the rear end surface of the endplate 213, an annular third shaft supporting surface 213 b capable of supporting a first thrust foil bearing 261 is formed.

In a rear housing 215, an annular thrust space 215 d recessed from the front end side toward rearward is formed. On the rear end side of the thrust space 215 d, that is, on the front end face in the rear housing 215, an annular fourth shaft supporting surface 215 b capable of supporting a second thrust foil bearing 263 is formed.

In the rear housing 215, a disk-shaped supporting plate 255 and first and second thrust foil bearings 261 and 263 are provided. The supporting plate 255 is press-fit into the rear end side of a rotating shaft main body 203 a. On the front end side of the supporting plate 255, an annular third shaft supported surface 255 a facing the third shaft supporting surface 213 b is formed. On the rear end side of the supporting plate 255, an annular fourth shaft supported surface 255 b facing the fourth shaft supporting surface 215 b is formed. The first thrust foil bearing 261 is provided between the third shaft supporting surface 213 b and the third shaft supported surface 255 a. The second thrust foil bearing 263 is provided between the fourth shaft supporting surface 215 b and the fourth shaft supported surface 255 b.

The rear housing 215 includes a columnar convex portion 215 a extending frontward from the rear in the rotational axis O direction. On the outer circumferential surface of the convex portion 215 a, a second shaft supported surface 253 b coaxial with the rotational axis O is formed.

On the outer circumferential surface on the rear end side in the rotating shaft main body 203 a, a first shaft supported surface 253 a facing the first shaft supporting surface 215 f is formed. The first radial foil bearing 257 is provided between the first shaft supporting surface 215 f and the first shaft supported surface 253 a. In the rotating shaft main body 203 a, a recessed portion 203 c extending frontward from the rear end is formed. The recessed portion 203 c has a cylindrical shape opened on the rear end side and is coaxial with the rotational axis O. The inner diameter of the recessed portion 203 c is larger than the diameter of the convex portion 215 a. The convex portion 215 a is inserted into the recessed portion 203 c. On the inner circumferential surface of the recessed portion 203 c, a second shaft supporting surface 215 e facing the second shaft supported surface 253 b is formed. A second radial foil bearing 259 is provided between the second shaft supporting surface 215 e and the second shaft supported surface 253 b. The other components in a turbo type compressor 200 are the same as the components of the turbo type compressor 100 in the embodiment 1.

In the turbo type compressor 200, a refrigerant flown in from the gap 214 s can flow into a space between the first shaft supported surface 253 a and the first shaft supporting surface 215 f, a space between the third shaft supported surface 255 a and the third shaft supporting surface 213 b, a space between the fourth shaft supported surface 255 b and the fourth shaft supporting surface 215 b, and a space between the second shaft supported surface 253 b and the second shaft supporting surface 215 e in order.

In the turbo type compressor 200, the first radial foil bearing 257 is provided on the first shaft supporting surface 215 f. The second radial foil bearing 259 is arranged in the recessed portion 203 c, which is the inner side of the first radial foil bearing 257. Therefore, portions where the dynamic pressure is generated in the first radial foil bearing 257 and the second radial foil bearing 259 radially overlap so that shaft length is not extended. The other action and effects in the turbo type compressor 200 are the same as the action and effects of the turbo type compressor 100 in the embodiment 1.

Embodiment 3

In a turbo type compressor 300 shown in FIG. 6, in a first shaft supporting surface 315 f of the rear housing 315, three first key grooves 315 g, 316 g, and 317 g, which extend in the rotational axis O direction, are recessed at equal intervals. The first key groove 315 g is located above the first shaft supporting surface 315 f. The first key groove 316 g is located on the lower right side of the first shaft supporting surface 315 f. The first key groove 317 g is located on the lower left side of the first shaft supporting surface 315 f. In a second shaft supporting surface 315 e of the rear housing 315, two second key grooves 315 h and 316 h, which extend in the rotational axis O direction, are recessed in symmetrical positions centering on the rotational axis O. The second key groove 315 h is located on the right side. The second key groove 316 h is located on the left side.

Three first radial foil bearings 356, 357, and 358 are provided between the first shaft supporting surface 315 f and the first shaft supported surface 53 a. The first radial foil bearings 356, 357, and 358 include first top foils 356 a, 357 a, and 358 a and first bump foils 356 b, 357 b, and 358 b. In the first top foils 356 a, 357 a, and 358 a, first keys 356 k, 357 k, and 358 k engaged in the first key grooves 315 g, 316 g, and 317 g are formed. The first keys 356 k, 357 k, and 358 k engage in the first key grooves 315 g, 316 g, and 317 g to thereby stop rotation of the first top foils 356 a, 357 a, and 358 a in the radial space 15 c. A gap 356 s slenderly extending in the front-rear direction is formed between the other end side of the first top foil 358 a and one end side of the first top foil 356 a. A gap 357 s slenderly extending in the front-rear direction is formed between the other end side of the first top foil 356 a and one end side of the first top foil 357 a. A gap 358 s slenderly extending in the front-rear direction is formed between the other end side of the first top foil 357 and one end side of the first top foil 358 a.

Two second radial foil bearings 359 and 360 are provided between the second shaft supporting surface 315 e and the second shaft supported surface 53 b. The second radial foil bearings 359 and 360 include second top foils 359 a and 360 a and second bump foils 359 b and 360 b. In the second top foils 359 a and 360 a, second keys 359 k and 360 k engaged in the second key grooves 315 h and 316 h are formed. The second keys 359 k and 360 k engage in the second key grooves 315 h and 316 h to thereby stop rotation of the second top foils 359 a and 360 a in the radial space 15 c. A gap 359 s slenderly extending in the front-rear direction is formed between one end side of the second top foil 359 a and the other end side of the second top foil 360 a. A gap 360 s slenderly extending in the front-rear direction is formed between the other end side of the second top foil 359 a and one end side of the second top foil 360 a.

The first keys 356 k, 357 k, and 358 k and the second keys 359 k and 360 k shift from each other by about 30° or by about 90° centering on the rotational axis O. Therefore, the first key 356 k, the rotational axis O, the second key 360 k, and the first key 357 k are respectively arranged such that the rotational axis O is absent on an imaginary straight line L2 that connects the first key 356 k, the second key 360 k, and the first key 357 k. The first key 356 k, the rotational axis O, the second key 360 k, and the first key 357 k are also respectively arranged such that the rotational axis O is absent on an imaginary straight line L3 that connects the first key 357 k and the second key 359 k. Further, the first key 356 k, the rotational axis O, the second key 360 k, and the first key 357 k are also respectively arranged such that the rotational axis O is absent on an imaginary straight line L4 that connects the first key 358 k, the second key 359 k, and the first key 356 k. The first key 356 k, the rotational axis O, the second key 360 k, and the first key 357 k are also respectively arranged such that the rotational axis O is absent on an imaginary straight line L5 that connects the first key 358 k and the second key 360 k. The other components in the turbo type compressor 300 are the same as the components of the turbo type compressor 100 in the embodiment 1.

In the turbo type compressor 300, when the first key 356 k and the rotational axis O are connected by an imaginary straight line, the gaps 359 s and 360 s of the second radial foil bearings 359 and 360 are absent on the imaginary straight line. When the first key 357 k and the rotational axis O are connected by an imaginary straight line, the gaps 359 s and 360 s are absent on the imaginary straight line. Further, when the first key 358 k and the rotational axis O are connected by an imaginary straight line, the gaps 359 s and 360 s are absent on the imaginary straight line. That is, the rotational axis O is absent on the imaginary straight lines L2, L3, L4, and L5 that connect the first keys 356 k, 357 k, and 358 k of the first top foils 356 a, 357 a, and 358 a in the first radial foil bearings 356, 357, and 358 and the second keys 359 k and 360 k of the second top foils 359 a and 360 a in the second radial foil bearings 359 and 360.

Therefore, in the turbo type compressor 300, even if the refrigerant flows out from the gaps 356 s, 357 s, and 358 s and the dynamic pressure of the refrigerant is less effective between the first shaft supported surface 53 a and the first top foils 356 a, 357 a, and 358 a, the dynamic pressure of the refrigerant acts between the second shaft supported surface 53 b and the second top foils 359 a and 360 a located on extended lines of the imaginary straight lines that connect the gaps 356 s, 357 s, and 358 s and the rotational axis O. In the turbo type compressor 300, even if the refrigerant flows out from the gaps 359 s and 360 s and the dynamic pressure of the refrigerant is less effective between the second shaft supported surface 53 b and the second top foils 359 a and 360 a, the dynamic pressure of the refrigerant acts between the first shaft supported surface 53 a and the first top foils 358 a and 359 a located on extended lines of the imaginary straight lines that connect the gaps 359 s and 360 s and the rotational axis O. Therefore, even if the second shaft supported surface 53 b of the second supported portion 53 in the rotating shaft 3 approach the gaps 359 s and 360 s of the second top foils 359 a and 360 a, the first shaft supported surface 53 a of the second supported portion 53 hardly approaches the gaps 356 s, 357 s, and 358 s of the first top foils 356 a, 357 a, and 358 a. The other action and effects in the turbo type compressor 300 are the same as the action and effects of the turbo type compressor 100 in the embodiment 1.

The present invention is explained above according to the embodiments 1 to 3. However, the present invention is not limited to the embodiments 1 to 3. It goes without saying that the present invention can be changed as appropriate and applied without departing from the gist of the present invention.

For example, in the embodiments, the turbo type compressors 100, 200, and 300 have the two stages of the compression phases by the first and second impellers 7 and 9. However, the turbo type compressors 100, 200, and 300 may have one compression process or may have three or more compression phases.

In the embodiments, the present invention can be embodied as a turbo type blower and the like besides the turbo type compressor.

Further, in the embodiments, other shaft supporting surfaces and other shaft supported surfaces may be further provided coaxial with the rotational axis O and on the rotational axis O sides or the outer circumference sides of the first and second shaft supporting surfaces 15 f, 215 f, 315 f, 15 e, 215 e, and 315 e and the first and second shaft supported surfaces 53 a, 253 a, 53 b, and 253 b. Other radial foil bearings may be further provided between the shaft supporting surfaces and the shaft supported surfaces.

In the embodiments, the first radial foil bearings 57, 257, 356, 357, and 358 including the one first top foil 57 a and the one first bump foil 57 b and the three first top foils 356 a, 357 a, and 358 a and the three first bump foils 356 b, 357 b, and 358 b are used. However, the first radial foil bearing may include two first top foils and first bump foils or may include four first top foils and first bump foils. As the second radial foil bearings 59, 259, 359, and 360, second bump foils including three or more second top foils and three or more second bump foils may be used. The first and second thrust foil bearings 61, 261, 63, and 263 including two or more first and second top foils and two or more first and second bump foils may be used.

Further, in the embodiments, the first and second rotation stop portions are not limited to the first and second keys 57 k, 356 k, 357 k, 358 k, 59 k, 359 k, and 360 k. Various rotation stop means can be adopted. For example, at least one of the first and second top foils 57 a, 356 a, 357 a, 358 a, 59 a, 359 a, and 360 a and the first and second bump foils 57 b, 356 b, 357 b, 358 b, 59 b, 359 b, and 360 b may be welded to the first and second shaft supporting surfaces 15 f, 215 f, 315 f, 15 e, 215 e, and 315 e to stop rotation of the first and second radial foil bearings 57, 257, 356, 357, 358, 59, 259, 359, and 360. At least one of the first and second top foils 57 a, 356 a, 357 a, 358 a, 59 a, 359 a, and 360 a and the first and second bump foils 57 b, 356 b, 357 b, 358 b, 59 b, 359 b, and 360 b may be fit in the first and second shaft supporting surfaces 15 f, 215 f, 315 f, 15 e, 215 e, and 315 e. The same applies to the third and fourth keys 13 k and 15 k of the first and second thrust foil bearings 61, 261, 63, and 263. 

1. A turbo type fluid machine comprising: a rotating shaft supported by a housing to be rotatable around a rotational axis; and an impeller coupled to the rotating shaft, wherein the turbo type fluid machine discharges fluid along with rotation of the impeller, wherein the rotating shaft includes a cylinder portion, and the rotating shaft is supported by a first radial foil bearing provided on a radially outer circumference of the cylinder portion and a second radial foil bearing provided on a radially inner circumference of the cylinder portion.
 2. The turbo type fluid machine according to claim 1, wherein the first radial foil bearing includes a first top foil and a first bump foil located on a radially outer circumference side of the first top foil and capable of elastically supporting the first top foil, the first top foil includes, at one end, a first rotation stop portion for preventing the first top foil from rotating with respect to the housing, the second radial foil bearing includes a second top foil and a second bump foil located on a radially inner circumference side of the second top foil and capable of elastically supporting the second top foil, the second top foil includes, at one end, a second rotation stop portion for preventing the second top foil from rotating with respect to the housing, and the rotational axis is arranged such that the rotational axis does not cross an imaginary straight line that connects the first rotation stop portion and the second rotation stop portion.
 3. The turbo type fluid machine according to claim 1, wherein the cylinder portion is provided at one end of the rotating shaft, the housing includes a bottomed cylindrical portion and a convex portion projecting into the cylinder portion from a bottom surface of the bottomed cylindrical portion, the first radial foil bearing is provided on a radially inner circumference of the bottomed cylindrical portion, and the second radial foil bearing is provided on a radially outer circumference of the convex portion.
 4. The turbo type fluid machine according to claim 3, wherein the cylinder portion includes a disk-shaped first supported portion extending from one end of the rotating shaft in a direction orthogonal to the rotational axis and a cylindrical second supported portion extending further apart from the one end of the rotating shaft from an outer circumferential edge of the first supported portion in parallel with the rotational axis, a first thrust foil bearing is provided on a surface of the first supported portion on the side of the rotating shaft, and a second thrust foil bearing is provided on a surface of the first supported portion on the opposite side of the rotating shaft. 